Allegedly, Cisco had this as official policy. They believed that by firing their lowest 10% after performance reviews every year, they would become a lean and mean beast. In practice, this sort of policy leads to the worst incentives for a business. Managers fight to protect friends at performance evaluation time who don't deserve it over those who are actually star workers, but less popular.
In practice, you lose people who are keeping the lights on and who hold vast organizational knowledge. Meanwhile, your entire company becomes physically-attractive subordinates.